Laminitis

Overview

Almost every horse owner and rider is familiar enough with the terms “founder” and “laminitis” to know it is a condition they hope to never have to experience. Laminitis is a unique condition to the horse and translates to inflammation of the laminae, the connective tissue of the hoof. The laminae hold the hoof wall to the coffin bone and during laminitis, inflammation causes the connections to become weak, resulting in painful separation of the hoof wall from the coffin bone. Laminitis can result from metabolic/endocrine disorders (Equine Metabolic Syndrome or Cushing’s disease), systemic inflammation (eg. diarrhea, grain overload), and/or mechanical forces (eg. excessive weight bearing on 1 limb due to injury of the other limb).

Signs & Symptoms

Typical clinical signs of laminitis include:

Sudden onset of severe lameness

Heat

Bounding digital pulses (increased pulses in the feet)

Most commonly, both front feet are affected, but horses can also develop laminitis in the hind feet or in a single limb. When the front feet are affected:

The horse typically rocks his weight back onto his hind limbs and extends both front legs.

The horse will usually be unwilling to walk forward or pick up either of his front feet. The discomfort may also manifest with horses treading from one foot to the other or walking gingerly on the affected feet (“walking on eggshells”).

A grading system called the Obel grading system has been established to describe the severity of clinical signs, ranging from Grade I (least severe, treading feet but not lame at the walk) to Grade IV (unwilling to move). In horses with laminitis associated with metabolic/endocrine disturbances such as Equine Metabolic Syndrome, the signs of laminitis may be much more subtle and sometimes subclinical. In these cases, it can be recognized from the development of rings on the hoof, called “laminitis rings” and chronic hoof issues, such as separation of the white line, without the classic acutely painful appearance of typical laminitis.

Diagnosis

A preliminary diagnosis is often made by an experienced horseman or veterinarian through observation of classic clinical signs and physical examination. Horses with laminitis are also typically sensitive to hoof tester pressure over the toe. Diagnosis can be confirmed through radiographs (X-rays), which can show sinking or rotation of the coffin bone. This sinking or rotation is from the degeneration of the laminae and loss of connection between the hoof wall and the coffin bone. Digital venograms can be used to visualize vasculature within the foot by injecting contrast into the veins and then taking radiographs. These are used to evaluate the level of blood perfusion to the foot and, therefore, prognosis for recovery.

Treatment

Laminitis can be treated using several possible modalities.

The first and most important would be the use of anti-inflammatories and pain medications, to combat the source of the inflammation, and pain. The most common medications used are non-steroidal anti-inflammatory drugs (NSAIDs) such as phenylbutazone (Bute).

An equally important modality of treatment is mechanical and supportive care. Deep bedding and cushioning of the foot alleviates the pain but also reduces concussive forces. A wedge may be applied to keep the heel higher than the toe, which alleviates tension from the flexor tendons. The combination of tension of the flexor tendons and weakened laminae can cause rotation of the coffin bone. In severe cases of laminitis, surgery is sometimes performed to cut the flexor tendon.

One of the findings during laminitis is decreased blood flow to the extremities. Medications such as acepromazine and pentoxifylline can be used to increase perfusion. Research and advancements in laminitis treatment are ongoing, with new medications, recommendations, and therapeutics being developed all the time.

Prognosis

Prevention and early treatment of laminitis constitute the best hope for recovery. Laminitis can be devastating due to intractable pain, severe sinking or rotation of the coffin bone, and/or loss of blood flow and perfusion to the foot. In the most severe cases, these factors can result in euthanasia. However, being familiar with the disease process, and recognizing risk factors and clinical signs early can sometimes prevent the worst from happening.

Radiographs are helpful for determining prognosis, as horses with less than 5 degrees of rotation of the coffin bone tend to have a good prognosis, while horses with greater than 15 degrees of rotation have a poor prognosis.

Prevention

About 90% of horses with laminitis have endocrine or metabolic disorders that can be identified prior to the development of clinical signs. For example, horses who are overweight or have regional areas of fat deposition can be tested and treated for Equine Metabolic Syndrome (EMS). Horses who are elderly and develop thick hair coats can be tested and treated for Cushing’s disease (aka PPID).

In the remaining 10% of horses, laminitis may be prevented by identifying high risk conditions such as grain overload, colitis (diarrhea), retained placenta, and enteritis (colic caused by small intestinal inflammation), and applying treatment before structural damage occurs. In these cases, horse are often treated with anti-inflammatory drugs and icing of the feet. Keeping the feet at about 4 degrees Fahrenheit may help prevent laminitis in these situations.

Conclusions

Although laminitis is scary and the consequences can be devastating, a greater understanding of the risk factors can help prevent an issue from occurring. Early identification of clinical signs can lead to more effective treatment and may save the life of your horse. If your horse tends to be an easy keeper, has suffered from a bout of laminitis in the past, or has other signs of EMS or Cushing’s disease, have a discussion with your veterinarian or a board certified internal medicine specialist and start reducing the risk now.